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Hi! New User-FIrst Post and a question about a '91(?) 9.9 Merc

N

NETim

New member
Hello all.

New here. I recently picked up a '91 9.9. (SN 0Cxxxxx). It seems to start and run okay. I haven't got a chance to test it thoroughly as the water here is starting to go solid.

Anyway, playing with it on the stand in the garage, I've noticed the choke knob has a definite "step" about halfway when pulling it out. The first half of the travel is relatively easy, then it hits a wall of sorts and I have to give it extra oomph to get the choke know fully pulled out. This phenomena seems worse when the knob is fully CW.

The linkage looks okay. I see nothing bent up anyway.

It does appear to have low hours on it as the plugs have black paint on them yet. Or it could be that it hasn't been well maintained. But the darn thing looks good. The plugs have a fair amount of carbon/soot on them but not eroded or worn in appearance. I'm going to throw a set of NGK's on it regardless.

The lower unit gear oil was milky/creamy in appearance. I have new gaskets on order for the vent and drain screws as they look old and aged. I am hoping the LU is okay. Fingers crossed.

I'm going to rebuild the water pump too.

Anyway, is that choke knob operation normal as I describe it?

TIA!
 
Welcome. You are on the right track. Water pump, spark plugs, and lower unit. Could have leaked out the drain, fill level plugs but likely it's a seal. When you have it apart for the water pump, you might want to bring in for a pressure test and vacuum test. I run about 15" of vacuum and 15 pounds pressure. Have all lower unit oil drained for the test and bring lower unit to room temperature. Turn shafts while testing to duplicate operating conditions. Closely examine prop shaft and all seals for obvious physical damage. If it doesn't hold pressure or vacuum, search for the leak area with soapy water. Make sure you never leave fishing line under prop or it may find its way to the seal and damage it. Also keep in mind to never tow the boat when the shifter is in neutral as the propeller will spin and dry out the outer lip of the seal and melt it. This is lubricated with water when normally operating in the lake or river.
As for the choke I think that sounds fairly normal to me where there is a warm up position for the choke and a fast idle adjustment as well. I'm just going on memory here perhaps another tech has more accurate information on that choke used for 1991.
 
Okay, thanks! Since I have 3 Mercs to maintain, I decided to go ahead and pick up one of those hand vacuum/pressure pumps with a gauge to test the lowers when I do the oil change. They're not that expensive and the peace of mind is priceless.

This little 9.9 was part of a package deal with a little Lund 14' that will be primarily used on small electric only pits and ponds locally. It will be very easy to launch and load on the soft primitive boat ramps. But the Merc will see use here and there. It just won't be making long distance trips to remote locations.

Thanks again!
 
There is no choke on that motor has a primer. Turn the knob all the way to the right for fast idle and warm up. Pull all the way out to squirt fuel into the motor ,and 1/2 out is like 1/2 choke
 
Right...right... thanks Mr. Scott. Got a few around here....pretty good system....when properly primed, often start first pull every time.
 
The "choke" knob is hard to pull out all the way because it takes some force to operate a lever that pushes down a button on the carburetor to prime it with a shot of gasoline. Rotating the knob to the right tightens the linkage that speeds up the idle. This only works in the "in position" and "halfway position". It advances the timing and keeps the engine running fast while warming up. It helps to understand this idle adjustment system in case you need to take the carburetor apart.
 
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